We present the results of the first observations, taken with
FLAMES during Science Verification, of red giant branch (RGB) stars
in the globular cluster NGC 2808.
A total of 137 stars was observed, of which 20 at high
resolution ( 47 000) with UVES and the others at lower resolution
( 19 000–29 000) with GIRAFFE in MEDUSA mode,
monitoring ~3 mag down from the RGB
tip. Spectra were taken of the Hα, Na i D and Ca ii H
and K lines.
This is by far the largest and most complete collection of such data in
globular cluster giants, both for the number of stars observed within one
cluster, and for monitoring all the most important optical diagnostics of
chromospheric activity/mass motions.
Evidence of mass motions in the atmospheres was searched from asymmetry in
the profiles and coreshifts of the Hα, Na i D and Ca ii K lines, as well as from Hα emission wings.
We have set the detection thresholds for the onset of Hα emission,
negative Na D2 coreshifts and negative K3 coreshifts at 2.5, 2.9 and 2.8, respectively. These limits are
significantly fainter than the results found by nearly all previous studies.
Also the fraction of stars where these features have been detected has
been increased significantly with respect to the previous studies.
Our observations confirm the widespread presence of
chromospheres among globular cluster giants, as it was found
among Population I red giants. Some of the above
diagnostics suggest clearly the presence of outward mass motions in the
atmosphere of several stars.

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